How to Tune up a Homelite String Trimmer ST-145

Replace the air filter after about 10 hours of use, and the spark plug as needed.

Like most small engines, your Homelite string trimmer is going to need a little TLC once in a while to keep it in good working condition. To tune up your ST-145 model, start by cleaning off the entire machine with a rag lightly soaked in water, paying special attention to vents or openings where grass and debris might have accumulated. Then take some time to replace the air filter and spark plug, which should result in a smoother-running machine.

1

Turn the trimmer's fuel cap to the left to open it.

2

Pour any fuel remaining in the tank into a gas can, using a funnel to ensure you don't spill any gas.

3

Pull off the spark plug cap at the top of the trimmer's engine.

4

Set a spark plug wrench over the top of the spark plug, and turn the wrench to the left to remove the spark plug. Homelite trimmers require a 5/8-inch deep socket wrench.

5

Insert a spark plug gap tool in between the thin metal protrusion at the top of the spark plug and the round section below it. Homelite string trimmers require a gap between these two parts of 0.025 inches. Slide the tool until it fits snugly between the two sections and determine how much gap is currently there. Tap the metal protrusion lightly with a hammer to reduce the gap, or press it upward to increase the gap by pressing upward with your tool. You'll know you have the right gap when the tool fits snugly between the two parts and is lined up with the "0.025" mark.

6

Slide the new spark plug into the hole and turn it to the right by hand. Further tighten the spark plug by turning it to the right with the spark plug wrench.

7

Replace the spark plug cap you took off before replacing the spark plug.

8

Pop off the air filter cover by snapping off the latch. The air filter cover, located near the trimmer's engine, should have the words "air filter" on it, making it simple to locate.

9

Pull out the existing air filter and discard it.

10

Set a piece of paper towel in your hand, and then lay the new air filter over top of that. In the other hand, hold an open bottle of SAE 10-30 oil. Press the air filter over the top of the bottle, tip the bottle and allow a small dot of oil to settle on the air filter.

11

Set the bottle of oil to the side and then squeeze the air filter and the paper towel into a ball, allowing the oil to distribute throughout the filter.

12

Replace the air filter and the air filter cover.

13

Lubricate any squeaky or stuck parts, such as the throttle, with a small dot of all-purpose lubricating oil.

Things You Will Need

Eye goggles

Nitrile gloves

Gas can

Funnel

Spark plug wrench

Spark plug gapping tool

All-purpose lubricant

SAE-30 motor oil

Paper towel

Tip

If the gas has been sitting in your trimmer for more than a few months, don't put it back into your trimmer -- that gas could damage your trimmer, and it's not worth putting it back in.